In general, in a combustion chamber of an internal combustion engine, a mixed gas is burned, and the internal combustion engine operates with energy occurring by a combustion heat.
An internal combustion engine is generally applied to an engine of a vehicle, and as the internal combustion engine, in order to increase the output of the engine and to reduce noise and a vibration, a multi-cylinder engine having a plurality of cylinders is generally used.
In such a multi-cylinder engine, an intake manifold, which is a path that guides an intake gas that is transferred from an intake path to each cylinder and an exhaust manifold, which is a path that collects an exhaust gas that is discharged from each cylinder and that transfers the exhaust gas to an exhaust path are mounted.
The intake manifold and the exhaust manifold are essential constituent elements of the multi-cylinder engine, and when air-tightness of the intake manifold and the exhaust manifold are not maintained, it may have a bad influence on stability and efficiency of the engine.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.